Assessing effects of permafrost thaw on C fluxes based on multiyear modeling across a permafrost thaw gradient at Stordalen, Sweden

[摘要] Northern peatlands in permafrost regions contain a large amount of organiccarbon (C) in the soil. Climate warming and associated permafrost degradationare expected to have significant impacts on the C balance of theseecosystems, but the magnitude is uncertain. We incorporated a permafrostmodel, Northern Ecosystem Soil Temperature (NEST), into a biogeochemicalmodel, DeNitrification-DeComposition (DNDC), to model C dynamics inhigh-latitude peatland ecosystems. The enhanced model was applied to assesseffects of permafrost thaw on C fluxes of a subarctic peatland at Stordalen,Sweden. DNDC simulated soil freeze–thaw dynamics, net ecosystem exchange ofCO₂ (NEE), and CH₄ fluxes across three typical land cover types,which represent a gradient in the process of ongoing permafrost thaw atStordalen. Model results were compared with multiyear field measurements, andthe validation indicates that DNDC was able to simulate observed differencesin seasonal soil thaw, NEE, and CH₄ fluxes across the three land covertypes. Consistent with the results from field studies, the modeled C fluxesacross the permafrost thaw gradient demonstrate that permafrost thaw and theassociated changes in soil hydrology and vegetation not only increase net uptake of Cfrom the atmosphere but also increase the annual to decadal radiativeforcing impacts on climate due to increased CH₄ emissions. This studyindicates the potential of utilizing biogeochemical models, such as DNDC, topredict the soil thermal regime in permafrost areas and to investigate impacts ofpermafrost thaw on ecosystem C fluxes after incorporating a permafrostcomponent into the model framework.

[学科分类] 地球化学与岩石